Compositions consisting essentially of graft copolymers of vinyl pyridine monomers on acrylonitrile polymers and method of preparing same

ABSTRACT

Dye-receptive graft polymers comprise a polyester polymer substrate having graft polymerized thereto units of an ethylenically unsaturated monomer which confers dye affinity to the resulting product, e.g. (a) vinyl lactam monomers, particularly vinyl pyrrdidones; (b) sulphonated alkenyl aromatic monomers and alkali metal salts or esters thereof; (c) sulphonated olefines and alkali metal salts or esters thereof; (d) sulphonated esters of acrylic and methacrylic acids and alkali metal salts or esters thereof; (e) sulphonated N-substituted acrylamides and methacrylamides and alkali metal salts or esters thereof; (f) vinyl pyridine and lower alkyl derivatives thereof; (g) amino-substituted alkenyl aromatic monomers; (h) aminoethyl acrylate and methacrylate and N-methyl and -ethyl derivatives thereof; (i) alkenyl aromatic monomers ar-substituted by polyglycol ethers; (j) polyglycol esters of acrylic and methacrylic acids; and (k) N-vinyl-3-morpholinone.  The grafting may be effected by impregnating the polyester with the monomer or a solution or dispersion thereof followed by polymerization of the monomer by means of a free radical catalyst or high energy irradiation, e.g. beta or gamma rays or the radiation from electron beam generators.  The polyester substrate is preferably in shaped form, e.g. a filament. The examples describe the grafting on to a polyethylene terephthalate substrate (cloth) of N-vinyl pyrrolidone, a mixture of N-vinyl pyrrolidone and 2-sulphoethyl methacrylate, 2 -vinyl pyridine, N-vinyl-3-morpholinone and a polyglycol monoacrylate.  The resulting products have good dye-receptivity.  Reference has been directed by the Comptroller to Specification 805,513.

g- 1962 G. w. STANTON ETAL 3,048,561

COMPOSITIONS CONSISTING ESSENTIALLY OF GRAFT COPOLYMERS OF VINYL PYRIDINE MONOMERS ON ACRYLONITRILE POLYMERS AND METHOD OF PREPARING SAME Filed Jan. 29, 1958 Ff/omen 7 006 ar/ic/e comp/13in; a gra/f/ capo/ymer 0/0 wng/ og r1 anve m on omer on an acry/on [/r /'/e oo/ymer subs zra/e.

INVENTORS. Gear 6 H S/an/on By Tea of; G. Tray/0r nrro g/vers COMPOSITEONS CONSHSTHNG ESSENTIALLY F GRAFT OOlQLYMERS 0F VlNYL PYRHDHNE MQNGMERS UN ACRYLONETRHLE POLYMERS El' METHGD 0F PREPAG SAME George W. Stanton, Walnut Creek, and Teddy (G. Traylor, Concord, Califi, assignors to The Dow Chemical Company, Midland, Mich, a corporation of Belaware Filed fan. 29, 1958, Ser. No. 711,933

8 (Claims. (Cl. IMG 4525) The present invention lies generally in the field of organic chemistry and contributes in particular to the art which pertains to synthetic, fiber-forming high polymers. More particularly, the present invention has reference to the provision of certain readily-dyeable graft or blocktype copolymers that are comprised of vinyl pyridine monomers polymerized on acrylonitrile polymer substrates.

Hydrophobic polymer materials of varying origin are commonly employed in the manufacture of various synthetic shaped articles including films, ribbons, fibers, filaments, yarns, threads and the like and related structures, which hereinafter will be illustrated with particular reference to fibers. Polymers and copolymers of acrylonitrile which contain in the polymer molecule at least about 80 percent by weight of combined acrylonitrile units may be utilized with great advantage for such purposes. Difficulty is often encountered, however, in suitably dyeing synthetic hydrophobic fibers and the like that have been prepared from acrylonitrile polymers, especially those that are comprised essentially of polyacrylonitrile. This is especially so when it is attempted to obtain relatively deeper shades of coloration in the finally dyed product.

Various techniques have been evolved for providing acrylonitrfle polymer compositions of improved dyeability. These included copolymerizing acrylonitrile with various monomeric materials which are intended to lend an enhanced dye-receptivity to the copolymeric product; blending polyacrylonitrile or other acrylonitrile polymers with one or more dye-receptive polymeric materials prior to formation of a fiber product or to the shaped article; and impregnating an already-formed acrylonitrile polymer fiber or other shaped article with a dye-assisting adjuvant or dye-receptive agent, which frequently maye be a polymeric material.

The practice of such techniques has not always been completely satisfactory. Neither have the products achieved thereby always provided a completely suitable solution to the problems involved. For example, many of the fiber products which are prepared in accordance with the above-identified techniques known to the art often have inferior physical properties when they are compared with those prepared from unmodified acrylonitrile polymers, particularly polyacrylonitrile. Also, such products, once they have been prepared, may not be as receptive as might be desired to a wide range of dyestuffs, due to inherent limitations in the materials capable of being employed for enhancing dye-receptivity. In addition, especially when textile fiber products are involved, treatment or modification of the acrylonitrile polymer article in any of the indicated known ways may not always permit uniform penetration of the dye throughout the cross-section of the fiber. Frequently, the articles (which have been modified according to known procedures may exhibit an undesirable tendency to accept a dyestuff only in their peripheral portions. When this phenomenon occurs (which, in connection with fiber products, is ordinarily referred to as ringdyeing), fibrillation of the fiber, such as normally results from its use, exposes the uncolored interior portions. Such behavior, of course, is undesirable and obriite fitate tent jectionable in fabrics and other textile materials constructed with fibers of the acrylontrile polymers.

It would "be advantageous, and it is the chief aim and concern of the present invention, to provide acrylonitrile polymers which have been modified with certain graft or block copolymerized substituents so as to be exceptionally dye-receptive while being capable of being fabricated into fibers and the like and related shaped articles having excellent physical properties and other desirable characteristics commensurate with those obtained with the unmodified acrylonitrile polymer substrates, and of the general order obtainable with unmodified polyacrylonitrile. This would possibilitate the manufacture of acrylonitrile polymer based fibers and the like articles having the highly desirable combination of attractive physical characteristics and substantial capacity for and acceptance of dyestuffs.

To the attainment of these and related ends, a dyereceptive polymer composition that is adapted to provide shaped articles having excellent physical properties and characteristics while being simultaneously receptive of and dyeable to deep and level shades of coloration with many of a wide variety of dyestuffs is, according to the present invention, comprised of a fiber-forming graft or block copolymer which is comprised or consists essentially of an acrylonitrile polymer substrate having a minor proportion of substituents graft copolymerized thereto consisting essentially of polymerized vinyl pyridine monomers. schematically, the compositions may be structurally represented in the following manner:

l o o o I I l I wherein the interlinked PVCN symbols represent the acrylonitrile polymer substrate or trunk and the symbols G connected thereto the substituent graft copolymers branches of the indicated vinyl pyridine monomer provided thereon.

As is apparent, the graft copolymer snbstituent that is combined with the acrylonitrile polymer substrate lends the desired receptivity of and substantivity for various dyestuffs to the compositions while the acrylonitrile polymer trunk substrate that is so modified facilitates and secures the excellent physical properties and characteristics of the various shaped articles, including fibers into which the compositions may be fabricated. Advantageously, as mentioned, the acrylonitrile polymer substrate that is modified by graft copolymerization to provide the compositions of the invention contains in the polymer molecule at least about percent by weight of combined acrylonitrile. More advantageously, the acrylonitrile polymer substrate consists substantially or essentially of polyacrylonitrile.

It is usually beneficial, as has been indicated, for the graft copolymer compositions of the present invention to contain a major proportion of the acrylonitrile polymer trunk or substrate that has been modified with the substituent dye-receptive graft copolymer groups chemically attached thereto. As a general rule, for example, it is desirable for the graft copolymer to be comprised of at least about 80 percent by weight of the acrylonitrile polymer substrate. In many instances, it may be satisfactory for the graft copolymer composition to be comprised of between about and percent by weight of the acrylonitrile polymer substrate, particularly when it is polyacrylonitrile. In this connection, however, better dyeability may generally be achieved when the grafted vinyl pyridine copolymer substituents are prepared under such conditions that they have relatively long chain lengths. Thus, it is usually preferable, when identical quantities of grafted substituents are involved for relascanner X Xl wherein one X is a vinyl (CH=CH radical and the remainder are independently selected from the group consisting of hydrogen and lower alkyl groups or radicals that contain from 1 to 4 carbon atoms. Typical of the monomers of those types that may be employed advantageously in the practice of the present invention are 2-vinyl pyridine; 4-methyl-2-vinyl pyridine; 4-vinyl pyridine; 2,4-diethyl-6-vinyl pyridine; 2-methyl-4-vinyl pyridine; and 4-tertiary butyl-2-vinyl pyridine. Advantageously, the vinyl pyridine monomers that are employed are 2-vinyl pyridine; 4-methyl-2-vinyl pyridine; and 4-vinyl pyridine. If desired, the monomers of the present invention may be utilized in combination or mixture with other Varieties of monomers in order to prepare mixed graft copolymers having specific properties and effects,

particularly with respect to their capability for accepting greater numbers of diverse types of dyestuffs. For example, the vinyl pyridine monomers provide graft copolymers showing an excellent acceptance of direct or acid type dyestuffs. However, other varieties of monomers such as those which may provide acidic chemical characteristics in the resulting graft copolymer structure may frequently be used with great advantage to enhance the dye-receptivity of the resulting product to basic types of dyestuffs. Such monomers as the various sulfonated vinyl aromatic monomers, sulfonated olefin monomers and sulfonated acrylate and methacrylate monomers may frequently be used in beneficial combination with the vinyl pyridine monomers contemplated herein.

As mentioned, the graft copolymer compositions of the invention have remarkably good dye-receptivity, particularly in view of their acrylonitrile polymer origin. In most cases, for example, the dye-receptivity of the graft copolymer compositions of the present invention is improved to such an extent in comparison with unmodified acrylonitrile polymers, particularly unmodified polyacrylonitrile, that a color differential of at least about 40 Judd units, as hereinafter illustrated, may readily be obtained between samples of the unmodified acrylonitrile polymer substrate and the graft copolymer compositions of the present invention, each of which have been dyed at a 4 percent dyeing, according to conventional techniques with such a dyestuff as Calcodur Pink 23L. This is a significant advantage when the compositions are fabricated into shaped article form, especially when they are prepared in a filamentary form suitable for use as a textile material.

The Judd unit is described by D. B. Judd in the American Journal of Psychology, vol. 53, page 418 (1939). More applicable data appears in Summary on Available Information on Small Color Difference Formulas by Dorothy Nickerson in the American Dyestuff Reporter, vol. 33, page 252, June 5, 1944. Also see Interrelation of Color Specifications by Nickerson in The Paper Trade Journal, vol. 125, page 153, for November 6, 1947.

As is well known, Calcodur Pink 2BL is direct type of dye that has a Color Index of 353. It is commercially obtainable under the indicated trade-designation. The same dyestuif, which is the sodium salt of 3,3-disulphodiphenylurea-4,4'-diazobis 2 amino 8 naphthol-6-sulfonic acid, is actually available (frequently under other commercial designations) from several sources. Calcodur Pink 2BL has the following structural formula, as is given on page 88, Section A, Part IV of the Colour Index (1st Ed., 1924) published by the (British) Society of Dyers and Colourists:

Recently, this dyestuff has been designated Colour Index Direct Red 75.

Besides having excellent physical properties and other desirable characteristics, fibers and the like articles comprised of the present compositions similarly have the indicated high capacity for being readily and satisfactorily dyed to deep and level shades of coloration with many dyestuffs. For example, fibers of the present compositions rnay be easily and successfully dyed according to conventional procedures using acid, vat, acetate, direct, naphthol, and sulfur dyes. Such dyestuffs, in addition to the particular variety mentioned, by way of didactic illustration, as Calcocid Alizarine Violet (Colour Index 61710, formerly Colour Index 1080), Amacel Scarlet BS (American Prototype Number 244), Sulfanthrene Red 313 (Colour Index Vat Violet 2), Naphthol ASMX (Colour Index 35527), Fast Red TRN Salt (Colour Index Azoic Diazo 11), and Immedial Bordeaux G (Colour Index Unknown or Unestablished) may advantageously be employed for such purposes.

Other dyestuffs, by way of further illustration, that may be utilized beneficially on fiber products of the dyereceptive graft copolymer compositions of the invention include such direct cotton dyes as Chlorantine Fast Brown CLL (Colour Index Unknown or Unestablished), Chlorantine Fast Green SBLL (Colour Index Direct Green 27), Chlorantine Fast Red 7B (Colour Index Direct Red 81), Pontamine Green GX Conc. 125 percent (Colour Index Direct Green 6), Calcomine Black EXN Conc. (Colour Index Direct Black 38), Niagara Blue NR (Colour Index Direct Blue 151) and Erie Fast Scarlet 4BA (Colour Index Direct Red 24); such acid dyes as Anthraquinone Green GN (Colour Index Acid Green 25), Anthraquinone Blue AB (Colour Index Unknown or Unestablished), Sulfonine Brown 2R (Colour Index Acid Orange 51), Sulfonine Yellow 2G (Colour Index Acid Yellow 40), Neutracyl Brown RD (Colour Index Unknown or Unestablished), Xylene Milling Black 2B (Colour Index Acid Black 26A), Xylene Milling Blue FF (Colour Index Acid Blue 61), Xylene Fast Rubine 3GP PAT (Colour Index Acid Red 57), Calcocid Navy Blue R Conc. (Colour Index Acid Blue 120), Calcocid Fast Blue BL (Colour Index Fast Blue 59), Calcocid Milling Red 3R (Colour Index Acid Red 151), Alizarine Levelling Blue 2R (Colour Index Acid Blue 51), Amacid Azo Yellow G Extra (Colour Index Acid Yellow 63); such mordant-acid dyes as Alizarine Light Green GS (Colour Index Acid Green 25) and Brilliant Alizarine Sky Blue BS PAT (Colour Index Acid Blue 129); such vat dyestuffs as Midland Vat Blue R Powder (Colour Index Vat Blue 35), Sulfanthrene Brown G Paste (Colour Index Vat Brown 5), Sulfanthrene Black PG Dbl. (Colour Index Unknown or Unestablished), Sulfanthrene Blue 213 Dbl. paste (Colour Index Vat Blue 5), and

Sulfanthrene Red 3B paste (Colour Index Vat Violet 2); Indigosol Green IB Powder (Colour Index Vat Green 1), a soluble vat dyestuff; such acetate dyes as Celliton Fast Brown 3RA Extra CF (Colour Index Dispersed Orange 5), Celliton Fast Rubine BA CF (Colour Index Dispersed Red 13), Artisil Direct Black BKZ (Disperse Dye-Mixture-Colour Index Unknown or Unestablished), Artisil Direct Navy BR (Disperse Dye-Mixture-Colour Index Unknown or Unestablished), Artisil Direct Red BBB and Celanthrene Red 3BN Conc. (Both Colour Index Dispersed Red 15), Celanthrene Pure Blue BRS 400 percent (Colour Index Dispersed Blue 1), Acetamine Orange 3R cone. (Colour Index Unknown or Unestablished) and Acetamine Yellow N (Colour Index Dispersed Yellow 32); B-Naphthol+2-chloro-4-nitroaniline, an azoic dye; such sulfur dyes as Katigen Brilliant Blue GGS High Conc. (Colour Index Sulf. Blue 9) and Indo Carbon CLGS (Colour Index Sulf. Blue 6); and premetalized dyestuffs including Cibalan Yellow GRL (Colour Index Acid Yellow 116) and Supralan Blue NB (Colour Index Unknown or Unestablished); and the like.

The dyed products, especially textile fiber products, are generally lightfast and are well imbued with good resistance to crocking. In addition, dyed textile fiber products comprised of the compositions of the invention exhibit remarkable washfastness, despite repeated exposure and subjection to washing, laundering and dry cleaning treatments. A shaped filamentary article prepared from a dye-receptive composition in accordance with the present invention is schematically illustrated in the sole figure of the hereto annexed drawing.

The dye-receptive graft copolymers of the present invention may be prepared and provided by impregnating the acrylonitrile polymer substrate with the monomeric substance then polymerizing the monomer in situ in the acrylonitrile polymer substrate. Advantageously, this may be accomplished when the substrate is in the form of an already shaped article, such as a fiber or filamentary structure. Beneficially, the graft copolymerization of the impregnated monomer may be accomplished and facilitated with the assistance of a polymerization catalyst or catalyzing influence which preferentially interacts with the substrate so as to establish or form a grafting site in order to simultaneously or subsequently initiate the graft copolymerization. As a practical matter, it is generally most desirable to form the graft copolymer compositions in such manner. Most of the free radical generating chemical catalysts, including peroxide and persulfate catalysts, may be utilized for the desired graft copolymerization. It may often be exceptionally advantageous, however, to accomplish the graft copolymerization by subjecting the monomer-impregnated acrylonitrile polymer substrate to a field of high energy radiation in order to efiiciently provide an effectively attached graft copolymer of the polymerized monomeric impregnate on the hydrophobic acrylonitrile polymer substrate. Thus, the graft copolymer compositions of the present invention may advantageously be provided in accordance with the general procedure that is described in copending application for United States Letters Patent of George W. Stanton and Teddy G. Traylor having Serial No. 553,701, filed December 19, 1955, disclosing a Process for Treating Shaped Polymeric Articles to Improve Dyeability.

The monomer may be intimately impregnated in the acrylonitrile polymer substrate in any desired manner prior to the graft copolymerization. Thus, the monomer may be directly applied or it may be applied from dispersion or solution in suitable liquid vehicles until a desired monomer content has been obtained. Ordinarily, it is advantageous for the monomer to be diluted in a solvent or dispersant vehicle so as to provide a treating bath in which to impregnate the acrylonitrile polymer substarte with the latter being immersed in the bath for a suificient period of time to attain a desired monomer content in the polymer substrate which, as has been mentioned, may be in any fabricated or unfabricated form. Unfabricated graft copolymer compositions in accordance with the present invention may be converted to shaped articles by any desired technique adapted for such purpose with conventional polymers. It is generally desirable and of significant advantage, however, to impregnate a preformed article, such as a textile fiber of the acrylonitrile polymer (or a cloth or fabric comprised thereof) with the monomers in order to prepare the graft copolymer compositions of the invention.

In this connection, particularly when preformed fiber structures are involved, the article may be in any desired state of formation for the impregnating and graft copolymerizing modification. Thus fibers and films may be treated before or after any stretch has been imparted thereto. In addition, they may be in various stages of orientation, or in a gel, swollen or dried condition. It is generally advantageous to prepare the compositions of the invention by impregnating the monomer into the acrylonitrile polymer substrate while the latter is in a waterswollen or hydrated aquagel condition, prior to being finally converted to a dried polymer structure. Such aquagels may be obtained by forming the shaped acrylonitrile polymer articles from the acrylonitrile polymer while it is dissolved in an aqueous saline solution thereof (such as a 60 percent by weight aqueous zinc chloride solution) as by coagulation in a suitable aqueous liquid bath capable of having such effect. When impregnating baths of the monomer are employed, it is generally desirable for them to have a monomer concentration of between about 0.5 and 50 percent by Weight and to be pre pared as an aqueous solution of the monomer. This is particularly the case when acrylonitrile polymers in an aquagel condition are being impregnated. The impregnation of acrylonitrile polymer fibers and related shaped articles from such a bath may be continued until between about 0.5 and 20 percent by weight of monomer, more or less, based on the weight of the acrylonitrile polymer substrate is incorporated in the substrate. Obviously, unfabricated polymers may be impregnated in an analogous manner. Ordinarily, an impregnating bath having a monomer concentration of between about 5 and 15 percent by Weight may advantageously be employed to impregnate the acrylonitrile polymer substrate with monomer in an amount between about 5 and 15 percent by weight of the polymer substrate.

The impregnation and succeeding polymerization may, in general, be effected at temperatures between about 0 C. and about 200 C. for periods of time ranging up to 4 or more hours. The most suitable conditions in each instance may vary according to the nature and quantity of the specific monomeric impregnant involved and the graft copolymerizing technique that is utilized. For example, when chemical catalysts are employed for purposes of forming the graft copolymer, a temperature of between about 50 and C. for a period of time between about 15 and 45 minutes may frequently be advantageously employed for the purpose. Under the influence of high energy radiation, however, it may frequently be of greatest advantage to accomplish the graft copolymerization at temperatures between about 20 and 60 C. utilizing relatively low dose rates and total dosages of the high energy for the desired purpose.

When the graft copolymer compositions are prepared from preformed or already shaped acrylonitrile polymer substrates that are successively impregnated with the monomer, which is then graft copolymerized in situ in the shaped article, excess monomer, if desired, may be squeezed out or removed in any suitable manner prior to effecting the graft copolymerization.

The chemical free radical generating catalysts which may be employed with greatest advantage in the preparation of the graft copolymer compositions of the present invention include hydrogen peroxide, benzoyl peroxide,

J cumene hydroperoxide, ammonium or potassium persulfate and the like. Such catalysts may be used in conventional quantities to effect the graft copolymerization. When they are utilized, it is of greatest benefit to incorporate them in the impregnating solution of the monomer that is used.

The high energy radiation which may be employed for inducing the graft copolymerization for the preparation of the graft copolymers of the present invention is of the type which provides emitted particles or photons having an intrinsic energy of a magnitude which is greater than the planetary electron binding energies that occur in the graft copolymerizing materials. Such high energy radiation is available from various radioactive substances which provide beta or gamma radiation as, for example, radioactive elements including cobalt 60 and cesium 137, nuclear reaction fission products and the like. If it is preferred, however, high energy radiation from such sources as electron beam generators, including linear accelerators and resonant transformers, X-ray generators and the like may also be utilized. It is beneficial to employ the high energy radiation in a field of at least about 40,000 roentgens per hour intensity. A roentgen, as is commonly understood, is the amount of high energy radiation as may be provided in a radiation field which produces in one cubic centimeter of air at C. and 760 millimeters of absolute mercury pressure, such a degree of conductivity that one electrostatic unit of charge is measured at saturation (when the secondary electrons are fully utilized and the wall effect of the chamber is avoided). It is most desirable, incidentally, to graft copolymerize all or substantially all of the monomeric impregnant to and with the acrylonitrile polymer substrate being modified in order to provide the compositions of the present invention.

For purposes of specifically illustrating, Without intending to thereby limit the invention, the following didactic demonstration is provided wherein, unless otherwise indicated, all parts and percentages are to be taken by weight.

Example 1 An oriented polyacrylonitrile aquagel fiber that contained about 1 part of polymer hydrated with about 2 parts of water was soaked for about minutes in a 10 percent aqueous solution of 2-vinyl pyridine containing about 0.25 percent of the solution weight of a detergent which was the dioctyl ester of sodium sulfosuccinic acid, an anionic surfactant (Aerosol OT). The wet fiber was then irradiated in the electron beam of a Van de Graaff generator at a rate of mrep. per minute until a total dosage of about 10 rnrep. of 2 million electron volts had been effected. The irradiated yarn was then washed thoroughly with water, dried, heat treated for 5 minutes at 150 C., scoured and then dyed for one hour at the boil in Sevron Brilliant Red 4G, a basic dye formerly known as Basic Red 4G (Colour Index Basic Red 14). A deep red shade of coloration was obtained. In contrast, the unmodified yarn could be dyed to only the faintest degree with the same dyestutf. The graft copolymerized fiber product was also dyed well to deep and level shades of coloration with Calcodur Pink ZBL, a direct type of dyestuif (Color Index 353); Calcocid Alizarine Violet, an acid type of dyestuff (Color Index 1080); and Amacel Scarlet BS, an acid or acetate type of dyestutf (American Prototype No. 244). Its reflectance value (as hereinafter defined) upon a 4 percent dyeing in the usual manner with Calcodur Pink ZBL was about 30.

The dyeing with Calcodur Pink ZBL was performed at the 4 percent level according to the usual procedure at which the fiber sample was maintained for about one hour at the boil in the dyebath which contained the dyestulf in about an amount equal to about 4 percent of the weight of the fiber. The dyebath also contained sodium sulfate in an amount equal to about 15 percent of the weight of the fiber and had a bath-to-fiber weight ratio of :1. After being dyed, the fiber was rinsed with water and dried for about 20 minutes at C. The dye-receptivity of the Calcodur Pink 2BL-dyed fiber (as indicated by its mentioned reflectance value) was evaluated spectrophotometrt cally by measuring the amount of monochromatic light having a wave length of about 520 millirnicrons from a standard source that was reflected from the dyed sample. The numerical value obtained was taken along an arbitrarily designated scale from O to 100. This value represented the relative comparison of the light that was reflected from a standard white tile reflector that had a reflectance value of 316 by extrapolation from the O to scale. Lower reflectance values are an indication of better dyereceptivity in the fiber. For example, a reflectance value of about 20 to 25 or so for acrylonitrile polymer fibers dyed with 4 pencent Calcodur Pink 2BL is generally considered by those skilled in the art to represent a degree of dye-receptivity that readily meets or exceeds the most rigorous practical requirements and is ordinarily assured of receiving general commercial acceptance and approval. Ordinarily unmodified polyacrylonitrile fibers of the same type used for the preparation of the graft copolymerized product generally have a reflectance value of about on the same numerical scale. Thus the improvement in dyereceptivity between the graft copolymerized fiber product of the present invention in comparison with unmodified acrylonitrile polymers was such that a color dilferential was about 50 Judd units were obtained between the dyed graft copolymer composition and the unmodified acrylonitrile polymer fiber.

Results similar to the foregoing may also be obtained when other of the mentioned varieties of vinyl pyridine monomers of the Formula I are utilized in place of those set forth in the above example and when graft copolymers are prepared with shaped articles or unfabricated forms of acrylonitrile polymers (including various copolymers) that are treated and irradiated in other than aquagel forms.

What is claimed is:

l. Dye-receptive graft copolymer composition consisting essentially of (1) a completely homopolyrnerized, orientable polyacrylonitrile substrate having chemically attached directly to carbon atoms in its chain, as graft copolymerized substituents thereon, a minor proportion of (2) a polymerized vinyl pyridine monomer of the formula:

wherein one X is a vinyl (-CH=CH radical and the remainder are independently selected from the group consisting of hydrogen and lower alkyl groups that contain from 1 to 4 carbon atoms.

2. The composition of claim 1, wherein said polyacrylonitrile substrate has up to about 20 percent by weight, based on the weight of the composition, of said graft copolymerized substituents attached thereto.

3. The composition of claim 1, wherein said polyacrylonitrile substrate has between about 5 and 15 percent by Weight, based on the weight of the composition, of said graft copolymerized substituents attached thereto.

4. The composition of claim 1, wherein said graft co-.

" polymerized substituents are comprised of polymerized 2- vinyl pyridine.

5. The composition of claim 1, wherein said graft copolymerized substituents are comprised of polymerized 4- methyl-Z-vinyl pyridine.

6. The composition of claim 1, wherein said graft copolymerized substituents are comprised of polymerized 4- vinyl pyridine.

7. A filamentary shaped article comprised of the com position set forth in claim 1.

8. Method for the preparation of a dyereceptive graft copolymer composition which consists essentially of polymerizing, as graft copolymer substituents, a minor proportion of a vinyl pyridine monomer of the formula:

wherein one X is a vinyl (CH=CH radical and the remainder are independently selected from the group con-.

sisting of hydrogen and lower alkyl groups that contain from 1 to 4 carbon atoms in the presence of preformed, completely homopolymerized, orientable polyacrylonitrile whereby a graft copolymer product of the polymerized vinyl pyridine monomer substituents attached to carbon atoms in the polyacrylonitrile chain is formed.

References Cited in the file of this patent UNITED STATES PATENTS 2,538,779 Harrison et a1 Jan. 23, 1951 2,688,008 Chaney et al. Aug. 31, 1954 2,837,496 Vandenberg June 3, 1958 10 2,838,470 Coover June 10, 1958 FOREIGN PATENTS 781,434 Great Britain Aug. 21, 1957 

1. DYE-RECEPTIVE GRAFT COPOLYMER COMPOSITION CONSISTING ESSENTIALLY OF (1) A COMPLETELY HOMOPOLYMERIZED, ORIENTABLE POLYACRYLONITRILE SUBSTRATE HAVING CHEMICALLY ATTACHED DIRECTLY TO CARBON ATOMS IN ITS CHAIN, AS GRAFT COPOLYMERIZED SUBSTITUENTS THEREON, A MINOR PROPORTION OF (2) A POLYMERIZED VINYL PYRIDINE MONOMER OF THE FORMULA: 